Single-ply sealed membrane roofing system

ABSTRACT

A single-ply roofing system comprising parallel strips of membrane (10) laid on a roof deck (14) with at least one side edge of each strip secured to the deck by mechanical fasteners (16), the side edges of contiguous strips being bonded together, each strip having transverse membrane flaps (11) secured to its undersurface at longitudinal intervals and the flaps being secured to the deck by mechanical fasteners (16).

TECHNICAL FIELD

The invention relates to roofing systems comprising strips of syntheticelastomeric membrane secured to a roof deck with the strip edgesoverlapped and bonded, providing a smooth, flexible and durable finishedsurface.

BACKGROUND ART

Built-up roofing systems have been used for many years on flat deckroofs. Originally, several layers of tar paper were laid by coating thedeck and applying paper strips with hot tar. Later, the tar paper wasreplaced by layers of felt or fibrous material and the hot tar wasreplaced by hot asphalt. In either case, each strip of paper or felt wasoverlapped about three-quarters of the width of the previous sheet sothat the completed roof was multi-ply system. In some cases a top layerof crushed stone or gravel ballast was applied to aid in resistinguplift forces.

Originally, no insulation layer was used and the temperature of the airinside a building helped to counter the contrasting outside temperatureand kept the membrane within a moderate temperature range. In recentyears rising fuel costs have made it desirable, if not necessary, to usea layer of insulation next to the roof deck. As a result the differencebetween temperatures inside and outside of the building was greatlyincreased both winter and summer, subjecting the built-up plies toincreased temperature ranges resulting in increased expansion andshrinking stresses causing cracking and splitting, and consequentleakage.

The labor cost of installing built-up roofs and the cost of asphaltsused in the strip material and in the application thereof have beenrapidly increasing in recent years. Consequently, cheaper materials havebeen used with the inevitable result that such roofs fail prematurelyand experience leakage problems within the first five years afterinstallation.

Moreover, the use of hot asphalt produces substantial amount of fumes,creating an objectionable pollution problem violating EPA regulations,and possibly state regulations in certain areas.

Various solutions to these problems have been suggested including thesingle ply membrane systems which generally utilize elastic rubber orplastic strips of various widths. The rolled strips are unrolled ontothe roof deck and attached to the deck by suitable adhesive ormechanical fasteners, or both, and seamed together at the edges. Hot taror asphalt is not usually required. The membranes being used, of which Iam aware, include synthetic elastomers or rubbers, and thermoplastics,reinforced and nonreinforced.

Essentially, three types of single-ply systems employing such membranesare being used. One is a fully adhered system wherein the membrane isadhesively secured to the entire surface area of the roof deck and theedges of the membrane strips or sheets are seamed, usually having theirmarginal edges overlapped and bonded.

The second type is a so-called loose-laid system in which the membraneis fastened only at the perimeter and held down over the entire area bya layer of ballast amounting to 10 to 15 pounds per square foot, toresist uplift forces.

The third type is a mechanically fastened system in which the membraneis secured to the deck at intervals with mechanical fasteners and theedges of the membrane strips are bonded together.

One variation of a mechanically fastened system utilizes numerousmechanical fasteners to secure the membrane at close enough intervalsalong the strip edges so that uplift forces are absorbed at thefastening points and no gravel ballast is required. Any of the fastenerswhich are exposed must be waterproofed at additional cost. Anothervariation is to use a large number of plastic disks or washersmechanically fastened to the deck at close intervals and apply adhesiveto the disks as the membrane is unrolled over them. The adherence of themembrane to the disks is relied upon to withstand uplift and no gravelballast is used.

The fully adhered single-ply system has numerous advantages over thebuilt-up roof system, including longer life, weatherability and greaterintegrity due to improved membranes, reduction of maintenance costs andelimination of hot asphalt. However, adhering the membrane to the entiredeck surface is a very expensive operation from the standpoint of laborand the high cost of a special adhesive which can be applied withoutheating. Moreover, most such adhesives can not be applied in highmoisture environments or in cold temperatures. The overall cost of thefully adhered single-ply system is generally more than the conventionalbuilt-up system. Further, error-free installation is required as errorsin one ply are not repaired or covered over by the additional plies asin built-up systems. Other problems include flex fatigue of the membraneand subsequent cracking due to continual stressing of the material inisolated areas due to daily expansion and contraction of the deck.

The loose-laid single-ply system using a top layer of ballast eliminatesthe material and labor cost of the special adhesive but is still quitelabor intensive. Moreover, many existing roofs have not been builtstrong enough to carry the additional weight of the ballast in additionto the other loading requirements. Accordingly, new roofs must bedesigned to support the required weight of the ballast amounting to 10to 15 pounds per square foot in addition to the other loads. Further,the ballast tends to concentrate the stress loads due to expansion ofthe roof deck, as in some areas the ballast does not move duringexpansion and contraction of the building, again concentrating thestress and causing flex fatigue of the membrane and premature failure.

Mechanically fastened single-ply systems without gravel ballast on topreduce the concentration of stress loads on the membrane, but in orderto withstand the uplift forces the membrane must be fastened to the deckat close intervals over the entire area, minimizing the areas ofmembrane not secured to the deck. If the strips of membrane are securedonly along the bonded side edges, the width of the strips should berestricted to a dimension (about 5-6 ft.) in order to ensure adequateresistance to uplift in the membrane between fastening locations.

Mechanically fastened single-ply systems utilizing plastic disksfastened to the deck at close intervals and coated with adhesive in situas the membrane is unrolled over them require additional labor inapplying the adhesive, as well as the added cost of the adhesive. Inaddition, the reliability of the adhesive can be decreased by long termheat and moisture exposure, causing premature wind uplift failure.

DISCLOSURE OF INVENTION

The present invention provides an inexpensive mechanically fastenedsingle-ply roofing system of improved durability under a wide range ofclimatic conditions, and capable of withstanding uplift forces withouttop ballast.

It is an object of the present invention to provide an improvedeconomically installed fastening system for a single-ply roofing systemwhich will withstand uplift forces and at the same time permit roof deckexpansion forces to dissipate over a large surface area of the roofmembrane.

Another object is to provide an improved single-ply roof deck coveringsystem which is adapted for use on roof decks of wood, metal, concreteand existing built-up roof decks, and on steep pitched decks as well asflat decks.

Another object is to provide an improved roof deck covering system whichenables transferring to the membrane fabricating plant a substantialamount of the labor normally performed on the roof deck, therebyincreasing efficiency and reducing labor cost, as well as assuringreliable product quality by providing better quality control, betterworking environment, and better trained labor.

A further object is to provide an improved fastening system whichpermits the use of wide rolls or strips of membrane thereby minimizingthe aggregate amount of heat bonding of the seams required on the roofdeck at the overlapped side edges.

A still further object is to provide an improved mechanical fasteningsystem in which each strip of membrane is provided with transverse flapson its under surface at close longitudinal intervals for attachment toth deck, and the longitudinal marginal edges of the strips aremechanically fastened to the deck and sealed together in situ.

Still another object is to provide an improved mechanically fastenedsingle-ply roofing system in which the transverse flaps of laterallycontiguous strips are staggered with respect to each other so as tointerrupt wind lift forces moving across the membrane.

These and other objects are accomplished by the improvements comprisingthe present invention, preferred embodiments of which are disclosedherein by way of example as representing the best known mode of carryingout the invention. Various modifications and changes in details ofconstruction and operation are comprehended within the scope of theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a partially unrolled membranestrip being fastened to a roof deck in overlapping relation to apreviously fastened strip.

FIG. 2 is an enlarged sectional view on line 2--2 of FIG. 1, showing themanner of securing one of the transverse flaps to the roof deck.

FIG. 3 is a schematic plan view of a portion of an unrolled strip ofincreased width.

FIG. 4 is a schematic plan view showing several strips laid side-by-sidewith their marginal edges overlapped and their transverse flapsstaggered.

FIG. 5 is an enlarged schematic perspective view showing a preferredmethod of sealing the overlapped marginal edges of contiguous strips.

PREFERRED EMBODIMENT OF THE INVENTION

The single-ply roofing system comprising the invention is adapted foruse with a variety of membrane materials including synthetic rubbers orelastomers such as Neoprene and ethylene-propylene-diene monomer (EPDM),and thermoplastic synthetic resins such as chlorinated polyethylene(CPE) and polyvinyl chloride (PVC). Such materials are available inthicknesses ranging from 0.030" to 1/16" or more.

I prefer to use a membrane of thermoplastic polymeric material whichcontains a minimal amount of plasticizer so that no material migrationof plasticizer occurs causing loss of flexibility over long periods ofuse. However, the particular composition of the membrane per se forms nopart of the invention. The membrane is preferably about 0.030" inthickness and is reinforced with synthetic fibers in order better toimprove puncture resistance and to withstand uplift forces. In thedrawings the thickness of the membrane is exaggerated for clarity.

As shown in FIGS. 1 and 2, the improved membrane strips 10 are providedat longitudinal intervals with transverse flaps 11 secured along theircontiguous portions to the underside of the strip. One end of each flapis preferably notched as indicated at 12 for a purpose to be describedand the secured contiguous portion 13 is coextensive with the width ofthe strip. As shown, these flaps may be formed when the strip is made upat the factory by overlapping longitudinal strip portions andheat-bonding or otherwise adhering the marginal overlapping portion 13of the upper strip to the contiguous portion of the lower strip, leavingthe flap 11 free and unsecured.

Obviously, the same result can be obtained by securing transverse stripsto the underside of a continuous longitudinal strip, in which case aportion of each transverse strip extending all along the flap portionwould be secured to the underside of the continuous strip, leaving theflap free and unsecured.

As indicated, the improved strips 10 are supplied in rolls R and areunrolled on the roof deck which may comprise a substrate layer ofinsulation board 14 over a deck 15 which may be wood, as shown, or metalor the like. As a strip is unrolled each successive flap 11 is fastenedto the deck at intervals by metal or other type of wellknown fasteners16 which extend through the insulation board 14 into the deck 15, andthe longitudinal edge of the strip opposite to the notched ends of theflaps is also fastened by fasteners 16 to the deck at intervals. Theopposite longitudinal edge of the strip is laid preferably overlappingthe fastened longitudinal edge portion of a previously laid stripindicated at 10'.

Referring to FIGS. 1 and 5, the overlapped longitudinal edge portion ofthe strip 10 is heat-welded or bonded to the fastened underlying edgeportion of the strip 10'. The amount of overlap may vary from about 2 to4 inches. The heat bonding may be done progressively using aconventional electric heat welder indicated generally at 18 whichapplies heat through a nozzle 19 to the overlapping edge portion ofstrip 10 and has a following roller 20 to aid in making a good bond. Thenotches 12 in flaps 11 are provided to ensure that the ends of the flapsdo not detract from making a leak-proof bond between the overlappingedge portions of the strips 10 and 10'. When the heat-bonding of theoverlapped longitudinal edge portions of the strips 10 is completed, allof the mechanical fasteners are completely covered, and hence nowaterproofing of any fasteners is required.

As indicated in FIG. 4, the parallel strips 10 are laid in such mannerthat the fastened flaps of laterally contiguous strips are staggeredwith respect to each other so as to intercept or interrupt the uplifteffect of wind lift forces moving across the roof deck. The preferredspacing between flaps on each strip usually should not be more thanabout five to six feet. The spacing can be varied depending uponstrength of fabric, holding characteristics of the fasteners used, andupon the uplift forces involved with a particular roof deck.Accordingly, with the flaps staggered, the strips can be increased inwidth to 10, 15, 20 or more feet and still maintain the requiredresistance to wind uplift. For convenience the strips 10 in FIGS. 1 and4 are shown relatively narrow, but in FIG. 3 a wider strip is indicated.

Because the width of the strips 10 can be substantially increased overwidths previously in use, the time and labor of the heat-welding of thefewer overlapped seams is greatly reduced, and since this is amanual-on-site operation a large amount of the installation cost issaved. In prior systems where the contiguous strips are mechanicallyfastened to the deck only at their overlapped edges, the strips shouldnot exceed more than about five feet in width in order to provideadequate resistance to wind uplift forces.

The present improved membrane strip and associated single-ply roofingsystem provides for rapid and economical installation with a minimum ofmanual heat-welding, and results in a leak-proof roof covering whichadequately resists wind uplift forces without requiring ballast anddissipates roof deck expansion forces. The improved system enables theuse of wide rolls of membrane, and is adapted for use on steep pitchedroof decks as well as flat decks.

I claim:
 1. The method of laying a single-ply sealed fiber-reinforcedmembrane covering over a roof deck comprising, providing rolls ofmembrane strips having transverse flaps of membrane substantiallycoextensive of width to said strips, one transverse edge portion of eachflap being secured to the undersurface of said strips at longitudinalintervals, unrolling the strips successively in parallel side-by-sidepositions on the deck with their marginal side edge portions contiguous,mechanically fastening successive flaps of each strip at transverseintervals to the deck, mechanically fastening at least one marginal edgeportion of each strip at longitudinal intervals to the deck, and bondingthe marginal side edge portions of the strips together.Iadd., thesuccessive flaps on laterally contiguous strips being staggered withrespect to each other..Iaddend. .[.2. The method as described in claim1, wherein the flaps are secured to the strips at intervals of aboutfive to six feet..]. .[.3. The method as described in claim 2, whereinthe successive flaps on laterally contiguous strips are staggered withrespect to each other..]. .[.4. The method as described in claim 1,wherein the successive flaps on laterally contiguous strips arestaggered with respect to each other..].
 5. The method as described inclaim 1, wherein one marginal side edge portion of each strip is lappedover and bonded to the mechanically fastened marginal edge portion ofthe next contiguous strip.
 6. The method as described in claim 5,wherein the flaps are secured to the strips at intervals of about fiveto six feet. .[.7. The method as described in claim 6, wherein the flapson contiguous strips are staggered with respect to each other..].
 8. Themethod .[.as described in claim 1, wherein.]. .Iadd.of laying asingle-ply sealed fiber-reinforced membrane covering over a roof deckcomprising, providing rolls of membrane strips having transverse flapsof membrane substantially coextensive of width to said strips, onetransverse edge portion of each flap being secured to the undersurfaceof said strips at longitudinal intervals, unrolling the stripssuccessively in parallel side-by-side positions on the deck with theirmarginal side edge portions contiguous, mechanically fasteningsuccessive flaps of each strip at transverse intervals to the deck,mechanically fastening at least one marginal edge portion of each stripat longitudinal intervals to the deck, and bonding the marginal sideedge portion of the strips together, .Iaddend.at least one end of eachflap .[.is.]. .Iadd.being .Iaddend.notched to clear the overlapped.[.marginal.]. edge portions of the strips.
 9. The method as describedin claim 8, wherein the successive flaps on laterally contiguous stripsare staggered with respect to each other.
 10. A single-ply roofingsystem comprising, parallel strips of fiber-reinforced membrane sheetinglaid undoubled on a roof deck with their longitudinal marginal edgeportions contiguous, mechanical fastener means securing at least onemarginal edge portion of each strip to the deck at longitudinalintervals, the marginal edge portions being bonded together, each ofsaid membrane strips having transverse membrane flaps at longitudinalintervals substantially coextensive to said strips in width onetransverse edge portion of each flap being secured to the undersurfaceof the strip, and mechanical fastener means securing said flaps to saiddeck at transverse intervals.Iadd., the successive flaps of contiguousstrips being staggered with respect to each other..Iaddend.11. Asingle-ply roofing system .[.as described in claim 10, wherein.]..Iadd.comprising, parallel strips of fiber-reinforced membrane sheetinglaid undoubled on a roof deck with their longitudinal marginal edgeportions contiguous, mechanical fastener means securing at least onemarginal edge portion of each strip to the deck at longitudinalintervals, the marginal edge portions being bonded together, each ofsaid membrane strips having transverse membrane flaps at longitudinalintervals substantially coextensive to said strips in width onetransverse edge portion of each flap being secured to the undersurfaceof the strip, and mechanical fastener means securing said flaps to saiddeck at transverse intervals, .Iaddend.at least one end of each flap.[.is.]. .Iadd.being .Iaddend.notched to clear the contiguous marginaledge portions of the strips.
 12. A single-ply roofing system asdescribed in claim 11, wherein the successive flaps of contiguous stripsare staggered with respect to each other.
 13. A single-ply roofingsystem as described in claim .[.12.]. .Iadd.10 .Iaddend.wherein saidflaps are spaced apart at intervals of about five to six feet.
 14. Asingle-ply roofing system as described in claim 13, wherein saidmembrane strips are at least 10 feet wide.
 15. A single-ply roofingsystem as described in claim 10, wherein one marginal edge portion ofeach strip is lapped over and bonded to the mechanically fastened edgeportion of the next contiguous strip.
 16. A single-ply roofing system.[.as described in claim 15, wherein.]. .Iadd.comprising parallel stripsof fiber-reinforced membrane sheeting laid undoubled on a roof deck withtheir longitudinal marginal edge portions contiguous, mechanicalfastener means securing at least one marginal edge portion of each stripto the deck at longitudinal intervals, the marginal edge portions beingbonded together, each of said membrane strips having transverse membraneflaps at longitudinal intervals substantially coextensive to said stripsin width one transverse edge portion of each flap being secured to theundersurface of the strip, and mechanical fastener means securing saidflaps to said deck at transverse intervals, one marginal edge portion ofeach strip being lapped over and bonded to the mechanically fastenededge portion of the next contiguous strip, and .Iaddend.at least one endof each flap .[.is.]. .Iadd.being .Iaddend.notched to clear theoverlapped mechanically fastened edge portion of the next contiguousstrip. .[.17. A single-ply roofing system as described in claim 16,wherein the successive flaps of contiguous strips are staggered withrespect to each other..]. .[.18. A single-ply roofing system asdescribed in claim 10, wherein the successive flaps of contiguous stripsare staggered with respect to each other..]. .[.19. A single-ply roofingsystem as described in claim 18, wherein said flaps are spaced apart atintervals no greater than five feet. .[.20. A single-ply roofing systemas described in claim 19, wherein said membrane strips are at least 10feet wide..]. .[.21. A single-ply roofing system as described in claim10, wherein said flaps are spaced apart at intervals no greater thanfive feet..]. .[.22. A single-ply roofing system as described in claim21, wherein said membrane strips are at least 10 feet wide..]. .Iadd.3.The method of laying a single-ply sealed fiber-reinforced membranecovering over a roof deck comprising the steps of:providing rolls ofmembrane strips having transverse flaps of membrane substantiallycoextensive of width to said strips, one transverse edge portion of eachflap being secured to the undersurface of said strips at longitudinalintervals; unrolling the strips successively in parallel side-by-sidepositions on the deck with their marginal side edge portions contiguous;mechanically fastening successive flaps of each strip at transverseintervals to the deck; staggering said successive flaps on laterallycontiguous strips with respect to each other; and, continuously bondingthe marginal side edge portions of the strips together..Iaddend..Iadd.24. A single-ply roofing system comprising:parallel strips offiber-reinforced membrane sheeting laid unrolled on a roof deck withtheir longitudinal marginal edge portions contiguous; each of saidmembrane strips having transverse membrane flaps at longitudinalintervals substantially coextensive to said strips in width; saidsuccessive flaps of contiguous strips being staggered with respect toeach other; the marginal edge portions being continuously bondedtogether; one transverse edge portion of each flap being secured to theundersurface of the strip; and, mechanical fastener means securing saidflaps to said deck at transverse intervals..Iaddend.